Definition check for even parity: “Even parity means that each protected group of bits (data plus parity) contains an even number of 1s.” Evaluate this statement.
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ACorrect
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BIncorrect
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CTrue only for 8N1 UART framing
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DDepends on voltage levels (TTL/CMOS)
Answer
Correct Answer: Correct
Explanation
Introduction / Context:Parity is a simple integrity check used from legacy serial links to memory systems. Even parity’s definition is central to building and reading parity generators/checkers and debugging communication issues.
Given Data / Assumptions:
- Single parity bit protects a data field.
- Even-parity scheme is specified.
- No multi-bit ECC is implied—just parity.
Concept / Approach:The parity bit is set such that the total number of 1s in the code word (data + parity) is even. This permits detection of any odd number of bit errors (most notably single-bit flips). The definition is independent of line coding, voltage levels, or framing formats.
Step-by-Step Solution:
Count ones in the data field.If count is odd → parity bit = 1 to make the total even.If count is even → parity bit = 0 to keep the total even.Therefore, the given statement reflects the standard definition.Verification / Alternative check:Example: data 11001010 has four ones (even) → parity 0; data 11001011 has five ones (odd) → parity 1.
Why Other Options Are Wrong:
Incorrect: Opposes the textbook definition.True only for 8N1: Parity definition does not depend on UART framing style.Depends on voltage: Logic levels do not affect parity math.Common Pitfalls:Assuming parity corrects errors (it detects many, not all); mixing parity with checksums/CRCs.
Final Answer:Correct